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We derive H{\alpha} fluxes for a large spectroscopic andphotometric-redshift-selected sample of sources over GOODS-North and South inthe redshift range z = 3.8-5.0 with deep HST, Spitzer/IRAC, and ground-basedobservations. The H{\alpha} flux is inferred based on the offset between theIRAC 3.6 {\mu}m flux and that predicted from the best-fit SED. We demonstratethat the H{\alpha} flux correlates well with dust- corrected UV star-formationrate (SFR) and therefore can serve as an independent SFR indicator. However, wealso find a systematic offset in the SFR_H{\alpha}/SFR_UV ratios for z ~ 4-5galaxies relative to local relations (assuming the same dust corrections fornebular regions and stellar light). We show that we can resolve the modesttension in the inferred SFRs by assuming bluer intrinsic UV slopes (increasingthe dust correction), a rising star-formation history or assuming a lowmetallicity stellar population with a hard ionizing spectrum (increasing theL_H{\alpha}/SFR ratio). Using H{\alpha} as a SFR indicator, we find anormalization of the star formation main sequence in good agreement with recentSED-based determinations and also derive the SFR functions at z ~ 4-8. Inaddition, we assess for the first time the burstiness of star formation in z ~4 galaxies on <100 Myr time scales by comparing UV and H{\alpha}-based sSFRs;their one-to-one relationship argues against significantly burstystar-formation histories. Further progress will be made on these results, byincorporating new results from ALMA to constrain the dust-obscured starformation in high-redshift UV-selected samples.

astrophysical journal/the astrophysical journal

Inferred H{\alpha} Flux as a Star-Formation Rate Indicator at z ~ 4-5:  Implications for Dust Properties, Burstiness, and the z = 4-8  Star-Formation-Rate Functions